Studies of the structure and function of avian oncornaviruses polypeptides are described which will provide detailed insight into the internal architecture of these viruses and to the mechanisms by which the virus is assembled at the host cell membrane. Studies of the amino acid sequence of Rous sarcoma virus (RSV) p12, the major structural protein of the ribonucleoprotein (RNP) core, will be completed, including determination of the disulfide bridges and identification of phosphorylated threonyl and seryl residues. Detailed studies of the quaternary structure of p12 in the RNP particle will be performed using bifunctional cross-linking reagents. These studies should provide detailed knowledge concerning the exact structure of the RNP complex. Limited structural analyses will be performed on intact and "nicked" p19 polypeptides from RSV and avian myeloblastosis virus to 1) determine the sequences adjacent to points at which it is cleaved by proteases and 2) determine whether or not the C-terminal amino acid sequence of avian oncornavirus p19 is homologous to the amino terminus of p30 from mammalian viruses as suggested from models of precursor processing. The association of p19 with other virion polypeptides will be assessed by chemical cross-linking studies to assess the possible role of p19 and the intact gs antigen precursor in viral assembly. The regulation of the synthesis and degradation of a troponin C like calcium dependent regulatory protein (modulator protein) will also be studied in order to assess its possible role in cellular transformation by oncogenic viruses. BIBLIOGRAPHIC REFERENCES: Vanaman, T. C., and Watterson, D. M. (1976). Calcium Dependent Regulatory Protein of Cyclic Nucleotide Metabolism in Normal and Transformed Cells. Fed. Proc. 35:1363. Herman, A. C., and Vanaman, T. C. (1977). Automated Micro Procedures for Peptide Separations. Methods in Enzymology, in press.